The present invention relates to an actuator, which is used to select knitting members such as selectors and needles that are assembled in a knitting machine.
A large number of needles are arranged in a needle bed of knitting machines including flat knitting machines, and a pattern knitting, such as knitting of a jacquard pattern or a design pattern, is affected by using a needle selecting means, which is provided in a carriage reciprocating over the needle bed, to select and operate needles according to knitting data. As for a selector actuator, which is to be assembled into the needle selecting means, there are two types; one wherein a selector corresponding to a needle being required for knitting is selected by energizing a magnetic coil pole to attract and retain the selector, and the other one wherein a selector corresponding to a needle being required for knitting is selected by energizing a magnetic coil pole to release attraction of the selector. The former is called an exciting hold type electromagnet, and the latter is called an exciting release type electromagnet, and the present invention covers the needle selecting means of the latter.
FIG. 7 shows a longitudinal sectional side view of a needle bed and a carriage of a flat knitting machine using exciting release type electromagnets for a selector actuator. FIG. 8 is a view of the above-mentioned selector actuator from the attraction site side. FIG. 9 is a sectional view along the line ixxe2x80x94ix of FIG. 8. FIG. 10 is a sectional view along the line xxe2x80x94x of FIG. 8.
Knitting members such as needles 102, needle jacks 103, select jacks 104 and selectors 105 are sidably loaded in a plurality of needle grooves provided in a needle bed 101. The selector 105 is kept between metal strips 107, 108 being inserted into the needle bed 101 and the select jack 104 and is inserted in the needle groove, and an elastic leg 109 of the selector 105 is compressed and a pole contact 113 of the selector 105, which is to be attracted by the selector actuator 111 is constantly pressed upwards from the selector actuator 111.
The selector actuator 111 is fixed to a bracket 122, which is provided at the lower end of a cam plate 121 of the carriage 120, by a flange 116 provided on a case 115, and attraction sites 141a, 141b of the selector actuator 111 are opposed to the pole contact 113 of the selector. When the carriage 120 reciprocates for knitting, a butt 125 of the selector 105 will be pushed into the needle groove by a selector return cam (not illustrated), which is provided on the cam plate 121 of the carriage 120 to oppose to the selector 105, against the upward press by the elastic leg 109 of the selector 105. As a result, the pole contact 113 is brought to a position wherein it is attracted and retained by the attraction sites 141a, 141b of the selector actuator 111. Under this condition, with shifting of the carriage 120, the pole contact 113 will be brought to a needle selecting part. When a contact pole of a selector corresponding to a required needle comes onto the magnetic coil poles of the first needle selecting part or the second needle selecting part, the magnetic coil poles will be energized to cancel a magnetic flux of a permanent magnet to release the pole contact 113 from the attraction sites. As a result, the butt 125 of the selector will come out above the needle bed to engage with a raising cam (not illustrated) for succeeding selectors and advance, and in turn, the selector will push up the selector jack to an intermediate position or an advanced position. Both the first and second needle selecting parts are provided with a dedicated raising cam. A degree of pushup of a selector of one raising cam differs from that of the other raising cam. The first raising cam pushes up the select jack to the intermediate position, and the second raising cam pushes up the select jack to the advanced position that is ahead of the intermediate position. With this arrangement, three-way knitting of knit, tuck and miss can be done within one course.
To make needle selection for three-way knitting, the selector actuator 111 is provided, in the case 115, with a first controlled attraction part 135 and a second controlled attraction part 136, wherein both the controlled attraction parts have magnetic coil poles in their magnetic circuits, and with three non-controlled attraction parts 137, 138, 139 having no magnetic coil poles in their magnetic circuits. The above-mentioned attraction parts have two ranks of flat attraction sites 141a (163a, 146a, 173a, 156a, 183a) and 141b (163b, 146b, 173b, 156b, 183b) on the side opposing to the pole contacts of the selectors.
The controlled attraction parts 135, 136 comprise permanent magnets 143, 153 provided at the base of the case 115, and magnetic coil poles 145a, 145b, 155a, 155b sandwiching said permanent magnets in between them and having coils 144a, 144b, 154a, 154b. The controlled attraction parts 135, 136 has attraction sites 146a, 146b, 156a, 156b (the first needle selecting part, the second needle selecting part) at the top ends of the magnetic coil poles. The non-controlled attraction parts 137, 138, 139 have permanent magnets 161, 171, 181 and side yokes 162a, 162b and center yokes 172a, 172b and side yokes 182a, 182b, said yokes sandwiching the permanent magnet in between. The top ends of these yokes are provided with attraction sites 163a, 163b, 173a, 173b, 183a, 183b. The respective attraction sites are magnetized by the permanent magnets provided for them. Of the two ranks of attraction sites, one rank is magnetized to be the north pole and the other rank is magnetized to be the south pole. Thin copper plates 190 are inserted between attraction sites of the attraction parts 135 through 139 to inhibit magnetic flux generated in the noncontrolled parts from leaking to the attraction sites of the adjacent controlled attraction parts, and in turn to allow the above-mentioned five attraction parts to form independent magnetic circuits. 140a and 140b denote protectors.
Needle selection of the conventional selector actuator 111 works as follows. The pole contact 113 of a selector is displaced against its press by a selector return cam provided on the carriage 120 to contact the attraction sites 141a, 141b of the selector actuator 111. In each of non-controlled attraction parts, magnetic flux flows from the attraction site of the yoke of the north pole side through the selector into the attraction site of the yoke of the south pole side to attract and retain the selector on the attraction sites. Under this condition, when the carriage 120 travels further and the pole contact 113 of the selector gets onto the attraction sites 146a, 146b or 156a, 156b of the first needle selection part or the second needle selection part, the magnetic coil poles will be energized to demagnetize them and release the selector from the attraction sites 146a, 146b or 156a, 156b. 
However, the magnetic flux quanta leaking from the respective attraction sites of the non-controlled attraction parts 137 through 139 vary with the numbers of selectors being attracted onto the respective attraction parts 163a, 163b, 173a, 173b, 183a, 183b. The smaller are the numbers of selectors being attracted, the greater are the magnetic flux quanta leaking from the attraction sites 163a, 163b, 173a, 173b, 183a, 183b. Some of the magnetic flux flows beyond the copper plates 190 into the attraction sites 146a, 146b, 156a, 156b of the adjacent controlled attraction parts 135, 136. As a result, to release the selectors, a greater electric current, which is determined by taking the magnetic flux leakage into consideration, is required. Conversely, the larger are the numbers of the selectors attracted, the smaller are the magnetic flux leakages from the attraction sites 163a, 163b, 173a, 173b, 183a, 183b. Thus, smaller electric currents will be applied. As the difference in the number of selectors being attracted depends on designs (needle selection patterns) such as a jacquard pattern or a design pattern, the variation in the number of the selectors being attracted can not be avoided. Accordingly, if the electric currents to be passed through the magnetic coil poles 145a, 145b, 155a, 155b are constant, some selectors that must be released from the attraction sites may not be released, causing needle selection misses.
To solve the above-mentioned problem, for example, in a needle selecting means, which is disclosed in Patent Opening Hei 9-241952 (U.S. Pat. No. 5,694,792), the number of selectors being attracted by a non-controlled attraction part is determined from the needle selection pattern, and this number is used to control the electric current that is to be passed through the magnetic coil poles to release the selectors. In a needle selecting means that is disclosed in Patent Opening Sho 62-263358 (U.S. Pat. No. 4,715,198), a sensor such as a Hall element for detecting the magnetic flux quantum in a controlled attraction part is provided near the attraction sites of magnetic coil poles opposing to selectors to measure the ever-changing magnetic flux quantum, and the measured value is fed back to determine the optimal demagnetizing conditions, and in turn to release selectors irrespective of the number of selectors being attracted.
In the former needle selecting means, however, as the electric current is controlled by considering the magnetic flux leakage, an extra electric current will be needed to cancel the magnetic flux leakage. This poses a problem that the required electric current is greater. In the latter case, as sensors are provided near attraction sites of the magnetic coil poles, the entire means will become greater in size, and feedback control is needed.
One object of the present invention is to provide a new selector actuator for knitting members of a knitting machine that does not require feedback control, with electric currents flowing through magnetic coil poles being kept constant irrespective of variations in the number of knitting members, such as selectors, attracted onto attraction sites.
The selector actuator of the present invention for selecting knitting members of a knitting machine, for example a flat knitting machine, includes:
at least one controlled attraction part having at least two magnetic coil poles, each having an attraction site formed at the top end thereof, and arranged in a first direction with a magnet in between them; and
a plurality of non-controlled attraction parts having at least two yokes, each having an attraction site formed at the top end thereof, and arranged in said first direction with a permanent magnet, for example a permanent magnet, in between them.
A direction substantially perpendicular to said first direction is defined as the second direction, and said plurality of non-controlled attraction parts are arranged in the second direction on both sides of said controlled attraction part, and said yokes have ends in said second direction.
A knitting member is released from attraction sites of the controlled attraction part by energizing the magnetic coil poles of the controlled attraction part so as to demagnetize the attraction sites of the controlled attraction part.
The selector actuator according to the invention is characterized in that at least one magnetic coil pole opposes to the ends of at least two yokes in said first direction.
Preferably, each of said non-controlled attraction parts are provided with three yokes of first, second, and third yokes, arranged in the first direction; at least two permanent magnets are arranged in between these yokes; said two permanent magnets are symmetrical in terms of magnetic pole arrangement in said first direction, with the second yoke at the center of said three yokes; one of said two magnetic coil poles is arranged to oppose to the ends of the first yoke and the second yoke; and the other one of said two magnetic coil poles is arranged to oppose to the ends of the second yoke and the third yoke.
Preferably, each of said non-controlled attraction parts has n yokes, n being greater than three, and nxe2x88x921 permanent magnets arranged in between said yokes, said controlled attraction part has nxe2x88x921 magnetic coil poles, and each of magnetic coil poles is arranged to oppose to the ends of at least two yokes in said first direction.
Preferably, the magnetic fields of the attraction sites of the respective magnetic coil poles upon energization are made substantially identical to each other by varying the number of coil turns from a magnetic coil pole to a magnetic coil pole or varying the electric current for energization from coil to coil.
According to the present invention, knitting members such as selectors are selected by being attracted at attraction sites of yokes of non-controlled attraction parts and by releasing or keeping the attractions at an attraction site of a controlled attraction part. Electric currents to coils of magnetic coil poles cancel a magnetic flux flowing from magnets to the attraction sites of the controlled attraction part, and release the attractions of the knitting members. A magnetic flux leaking from the yokes to the magnetic coil poles poses a problem. A degree of the magnetic flux leakage is varied according to the number of knitting members attracted by yokes. In the present invention, magnetic coil poles oppose, for example near its attraction sites, to the ends of two yokes in the first direction. Because of this arrangement, the magnetic flux leakage flows in the magnetic coil poles in a direction substantially perpendicular to a direction of attracting the knitting members at the attraction sites of the magnetic coil poles, and does not affect the attractions of the knitting members. The perpendicular direction is substantially parallel to the first direction, and the direction of magnetic flux attracting the knitting members is substantially perpendicular to the plane that is determined by the first direction and the second direction. Hence the electric currents to the coils of the magnetic coil poles may be determined independently of the number of the knitting members attracted to yokes of the non-controlled attraction parts, and in turn there is no need of monitoring the number of the knitting members attracted.
It is desirable to provide magnetic coil poles, near their attraction sites, with plates of nonmagnetic materials such as copper, aluminum and plastics as magnetic resistance. In the present invention, as the magnetic flux leakage does not affect the attraction of the knitting members at the magnetic coil poles, the magnetic resistance value may be reduced, and the attraction forces of the yokes near the magnetic coil poles may be raised. This is advantageous in accurately selecting knitting members in a fine-gauge knitting machine wherein thicknesses of knitting members are small.
However, it is not desirable to pass a magnetic flux leakage that is as high as that prevent attractions of knitting members at yokes. It is desirable to increase magnetic resistance between yokes and magnetic coil poles rather than magnetic resistance between yokes and knitting members.